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On Sept. 29, Harvard Psychology professor Steven A. Pinker sat down at the First Parish Church to discuss his most recent book, “When Everyone Knows That Everyone Knows…: Common Knowledge and the Mysteries of Money, Power, and Everyday Life.” Published on Sept. 23, the book deals with the phenomenon of common knowledge — that is, when one knows that someone else knows that one knows something. Complicated though it may seem, it affects much of human interaction, according to Pinker.

“I explored a number of hypotheses, but one that really caught my fancy is the possibility that direct speech, blurting something out, generates common knowledge,” Pinker said, in conversation with Harvard Professor of Political Science Danielle Allen. “Someone says something, you know what they said, they know, you know, and etc.”

Direct speech, however, is often avoided in favor of euphemism. Euphemism obfuscates the message to avoid the creation of common knowledge.

Pinker gave the example of a man at the end of a date, who, instead of explicitly asking his partner to have sex with him, asks her to join him for a cup of coffee. Because he did not use direct speech, he avoids creating common knowledge and allows them both to plausibly deny the real meaning of the question.

Having avoided creating common knowledge that she rejected a sexual overture, they can revert back to their previous social relationship.

“Whereas if he had blurted out, ‘Hey, do you want to come up and have sex?’ then she would know that he would know that she would know that he would know for as many cycles as you want, and that would destroy the possibility of them resuming their previous social relationship,” Pinker said.

The same phenomenon works in many other kinds of human interactions. For example, if a driver pulled over by the police explicitly offers a bribe, that would create common knowledge that undermines the power of the police officer, according to Pinker.

“By blurting it out, you’re shattering the relationship that says the cop is in a position of authority over the driver,” Pinker said.

One attendee, Matt A. Johnson, who works at the Harvard Division of Continuing Education, said he came to Pinker’s book talk because of Pinker's academic reputation.

“I think Steven Pinker is probably on a Mount Rushmore of kind of public intellectuals,” Johnson said.

In Pinker’s talk, Johnson was interested in the idea of linguistic ambiguity.

“Some of the purposes of having language, which is open ended, means that it can be read in different ways. You get a little bit of tension there, right? You say something, and it’s interpretable in different ways,” Johnson said.

Mariam Motamedi, a first year graduate student at Harvard’s Graduate School of Education, said Pinker’s talk made her wonder how common knowledge affects pedagogy.

“It’s definitely relevant, because, thinking about educational spaces and accessibility in educational spaces, who knows what the norms are in a given space and what are the things that we take for granted, right?” said Motanedi. “This idea of common knowledge is, ‘I would assume that you know this thing,’ but if you don’t, then maybe I’m putting up barriers to access for you to take advantage of a certain space in a way that others would.”

Another member of the audience, Devang Sehgal also found the concept of common knowledge to be applicable to the field of medicine, as patients are often uncertain about new technologies.

“I work in the medical field, and I think people are somewhat uncertain about new technologies, but they’re more receptive when they know that other people have taken them,” Sehgal said. “If they know that other people have taken it, and they’re fine, I think that sort of gives them more confidence.”

Will S. L. Norton, another attendee, considers common knowledge a widely applicable concept.

“I think that definitely draws on the fact that you can see it across every aspect of life, if you look for it,” Norton said.

As Pinker’s book makes its way into reader’s hands, it is sure to make readers realize how common common knowledge truly is.

—Staff writer Alexandra M. Kluzak can be reached at alexandra.kluzak@thecrimson.com.